Check this site out....www.batterystuff.com/kb/tools/solar-calculator.html
looks like it does all the "slide rule stuff" for you... and you get to just play with the conditions of your system. (looks kind of like playing with Palmer's water spread sheet, or beersmith)
One thing to note... In your previous post, you had noted you had 6volt batteries.... and my spidey sense is going off.
Long story short, you likely have a 24V system... not 6V. I point this out because any amperage gauges you have are likely based on the 24V(assuming) not 6V.
6 Volt batteries are common in a power bank system, but usually what happens is that the batteries are hooked up in such a way (series) so that you get 12, 18 or 24V systems. (picture 4 batteries connecteced like this: -+ -+ -+ -+ that gives you a 24V system. 6+6+6+6) Likely you have a LOT of banks of batteries in parallel ... so lots of banks of 4 batteries in parallel, to give you the storage capacity you need, and larger amp capacity.
hopefully the site will allow for an easy estimation of time. If you get some funny results, I am happy to provide a reality check.